File system of FAT (File Allocation Tables) format store file data into a plurality of clusters which are divided, and manages the data of the file based on chain information between the clusters. The file system of the FAT format uses a boot sector area, a FAT area, and a file/directory area.
The boot sector area has information of the entire storage medium (capacity and cluster size of the storage medium, etc.). The file/directory area has data of the directory entry and the file. The file/directory area is divided into a cluster which is a unit area, and is managed. The directory entry includes information about the file name and the file size, etc. Further, the FAT area has the chain information of the clusters which constitute the data of the file.
Specially, the FAT area has FAT entry having management information of the cluster to every cluster. When there is a following data of a cluster to one data, the management information indicates an ID (Identification) number of the cluster that following data is memorized. In addition, when there is not the following data of the cluster, the management information indicates an EOC (End Of Cluster) and indicates the value indicating a space when the data is not memorized in corresponding cluster. In addition, the management information indicates a defective cluster when the corresponding cluster is a defective cluster.
In addition, in the FAT formats, there is the type such as FAT12 format, FAT16 format, FAT32 format, and exFAT (Extended FAT) format, for example. Depending on the type of the FAT format, the size of the FAT entry is different. For example, the size of the FAT entry of the FAT12 format is a 12 bit, and the size of the FAT entry of the FAT16 format is a 16 bit. In addition, the sizes of the FAT entries of the FAT32 format and the exFAT format are 32 bit.
Accordingly, the controllable maximum size of the recording medium grows big by increasing the number of the controllable clusters according to an expansion of the size of the FAT entry. For example, it is possible that the file system of the FAT32 format manages the recording medium which has bigger file than that of the file system of the FAT16 format.    [patent document 1] Japanese Laid-open Patent publication No. 2003-030969.    [patent document 2] Japanese Laid-open Patent publication No. 2004-013276.